1. Field of the Invention
The present invention is directed to a passive fan blade for a cooling package for use in an agricultural combine, particularly, it relates to keeping faces of a radiator and a charged air cooler clean of debris.
2. Description of the Related Art
An agricultural combine typically includes a cooling package which may include a radiator and a charged air cooler, each of which has a heat exchanger core with an upstream face, mounted into a frame. The cooling package circulates air through a heat exchanger core in the radiator to reject heat from the engine and other working parts of a combine, and through a heat exchanger core in the charged air cooler to cool air compressed in a turbocharger to make it more dense and allow more oxygen to be fed to cylinders of a engine. An agricultural combine provides a unique problem because of the environment it is in. In the hot environment of a combine, it is necessary to circulate a large volume of air through the cores to reject the large amount of heat produced by the engine, and to push as much air into the cylinders to get as much power out of the engine as possible. Because the environment of a combine is filled with dust and chaff, inevitably the dust and chaff will build up on the upstream faces of the heat exchanger cores, blocking a path of air flow. As the upstream faces become more and more blocked, heat transfer efficiency decreases. The decrease in heat transfer efficiency can lead to engine overheating and loss of power.
Previous attempts to alleviate the problem have included attempts to use passive fan blades immediately upstream of the front faces of the heat exchanger cores.
A passive fan blade acts to break up the debris that forms on the face of the core by making the air more turbulent at the face. It is called xe2x80x9cpassivexe2x80x9d because it is not driven by anything other than the passage of air over the blade, the air being drawn by a powered fan on the downstream end of the cooling package. Passive fan blades have included regions that are angled toward the downstream direction of air flow. The angled regions of the fan blades have caused the blades to rotate in response to the air flow.
The addition of passive fan blades has aided in keeping the heat exchanger core faces clean, however, the fan blades have not rotated dependably and reliably and in some cases have failed to rotate altogether. When the blades have rotated, they have not created enough turbulence to keep the upstream faces of the cores clean for a substantial period of time. It has been necessary to clean the cooling package so frequently that a farmer who is harvesting crops would have to stop several times a day to clear out the upstream face of the cooling package.
Although placing passive fan blades in front of the faces of the heat exchanger cores has assisted in the breaking up the debris and keeping the faces clean, the passive fan blades have not dependably and reliably provided enough turbulence to allow a farmer to continually harvest crops for an extended period of time.
Therefore, what is needed is a passive fan blade and system that will create enough turbulence to allow the upstream face of the heat exchanger cores to remain relatively clean for a full day of harvesting.
It is an object of the present invention to provide a passive fan blade for a cooling package for an agricultural combine that will reliably rotate at a predetermined rotational speed and provide enough turbulence to maintain a relative clean upstream face of a radiator and a charge air cooler of the cooling package.
It is another object of the present invention to minimize a clearance distance between a passive fan blade and upstream faces of the radiator and the charge air cooler of the cooling package.
It is another object of the present invention to provide a set of bearings for a passive fan blade that allows the fan blade to spin at the predetermined rotational speed that creates a high turbulence at the upstream faces of the radiator and the charge air cooler for the cooling package.
It is a feature of the present invention to provide a passive fan blade for cleaning upstream faces of a radiator and a charge air cooler for a cooling package of a combine. It has been determined that important factors that establish turbulence on the upstream face of the heat exchanger cores are rotational speed of the passive fan blades, clearance distance from the fan blade to the upstream face of the heat exchanger cores where the smaller the clearance distance, the more turbulence is created, and bearings that allow the fan blade to turn. To accomplish a desired level of turbulence, what is needed is a passive fan blade with a clearance distance as small as possible, a rotational speed that maximizes turbulence, and a set of bearings that maximizes turbulence.
The passive fan blade includes a rectangular-shaped member which has a center, a length and a width where the length is substantially greater than the width, an axis passing perpendicularly through the center of the member, and a mounting area generally at the center of the member. The mounting area has one larger hole for mounting a bearing housing described later, and a plurality of smaller mounting holes for receiving mounting bolts for a bearing assembly described later. The member is defined by two diametrically opposed legs, each with a middle region generally perpendicular to the direction of air flow, a leading region having an edge and a trailing region having an edge. Both the leading regions and the trailing regions are angled toward the downstream direction of airflow with respect to the middle regions, where the angles are between about 15 and about 30 degrees, with a preferred angle being about 20 degrees. The leading regions decrease in width as a distance from the axis is increased until it reaches a minimum width near the distal end of about 3% to about 15% of the total width of the member with a preferred width of the leading region at its minimum being about 11% of the total width of the member. The trailing regions increase in width as a distance from the axis is increased until it reaches a maximum width near the distal end of about 35% to 50% of the total width of the member with a preferred width of the trailing region at its maximum being about 45% of the total width of the member. As air flows past the member, a greater force is imparted on the trailing regions than on the leading regions, causing the fan blade to rotate in the direction of the leading regions.
One or two passive fan blades may be attached to a bracket having an upstream surface, and a downstream surface. Each blade has a corresponding hub that is generally of a cylindrical shape and is attached to the downstream surface of the bracket. A bearing assembly is attached to each hub using a set of mounting hardware, the bearing assembly having a set of bearings, and a bearing housing with a cover. The mounting hardware is also used to attach the bearing assembly to the mounting area of the member of the fan blade. The bearings within the bearing assembly allow the fan blade free rotation as air is passed over the fan blade. Bearing assemblies are chosen so that the fan blades rotate at a predetermined rotational speed, the rotational speed corresponding to a maximum turbulence. Rotational speeds of between about 200 rpm and about 800 rpm have been experimentally determined, with the present embodiment of this fan blade, to be an ideal range of rotational speeds, with a preferred rotational speed of about 400 rpm.
The cooling package of a combine may include a frame having outer walls that define an opening within the frame, a radiator with an upstream face, and a charge air cooler with an upstream face, wherein the radiator and the charge air cooler are mounted within the opening in the frame. Two fan blade assemblies are attached to a frame of the cooling package, the bracket of each fan blade assembly being attached to the frame. One bracket is positioned upstream of the radiator of the cooling package, and one bracket is positioned upstream of the charge air cooler. In one embodiment of the invention, the radiator fan blade assembly has one fan blade and the fan blade assembly of the charge air cooler has two fan blades. There is a clearance between the upstream face of the radiator and the radiator fan blade assembly and clearance distances between the upstream face of the charge air cooler and the charge air cooler fan blade assembly.
In an alternate embodiment of the invention, the radiator fan blade assembly has two fan blades and the charge air cooler fan blade assembly has two fan blades. Clearances for the radiator fan assembly are between the upstream face of the radiator and each fan blade of the radiator fan blade assembly. Clearances for the charge air cooler fan blade assembly are between the upstream face of the charge air cooler and each of the fan blades of the charge air cooler can blade assembly.
The clearances of both embodiments can be between 20 mm and 30 mm, with a preferred clearance of about 25 mm.